strip trailing '/' off of directories

Because GNU Make works on strings.  So "foo/" is NOT the same
as "foo", even though they both point to the same directory.

scripts/install.mk

@@ -128,7 +128,7 @@ define ADD_INSTALL_RULE.file
     install: ${2}
 
     # Install the file
-    ${2}: ${1} | $(dir ${2})
+    ${2}: ${1} | $(patsubst %/,%,$(dir ${2}))
 	@$(ECHO) INSTALL ${1}
 	$(Q)$${PROGRAM_INSTALL} -c -m 644 ${1} ${2}